CentOS was acqui-hired because Red Hat's upstream for layered products (at the time mostly RDO/OpenStack and oVirt/RHEV) could not use Fedora because it was too far from RHEL a year of two after RHEL was released, could not use RHEL because upstream contributors would have to pay, and could not use CentOS because its releases had too large delays. The solution was to make CentOS releases happen timely by paying people to make them.
These days a RHEL downstream is not enough for the layered products. Some of them require the kind of bleeding edge feature that is backported every six months to the RHEL kernel, and corresponding userspace changes (BPF, virtualization, etc.) and cannot afford waiting for the CentOS release because development must be done in parallel with RHEL. So the solution was to move CentOS from happening after RHEL to before RHEL which is what CentOS Stream is.
I can confidently say that the reasons are technical because other CentOS downstream have the same needs (e.g. Facebook's) and they also want to send patches to CentOS for bugfixes or features themselves, instead of waiting for Red Hat to find out about that bug, or decide they need the same feature. Plus there's no reason for rebuilds to disappear. The SRPMs will still be released by Red Hat.